Spatial Join

Definition

The spatial join is one of the core operators in spatial database systems. Efficient spatial join evaluation is important, due to its high cost compared to other queries, like spatial selections and nearest-neighbor searches. A binary (i.e., pairwise) spatial join combines two datasets with respect to a spatial predicate (usually overlap/intersect). A typical example is “find all pairs of cities and rivers that intersect.” For instance, in Fig.
1 the result of the join between the set of cities {
c1,
c2,
c3,
c4,
c5} and rivers {
r1,
r2}, is {(
r1,
c1), (
r2,
c2), (
r2,
c5)}.